A transflective color liquid crystal display is generally configured to have a semi-reflection layer as a thin layer made of, e.g., aluminum provided on one of the substrates and color filters provided on the semi-reflection layer or the other substrate.
There has been known a method wherein a full reflection layer is utilized in place of the semi-reflection layer, and that the full reflection layer has openings formed in some portions thereof. This method will be explained, referring to FIG. 3. A full reflection layer 2 is deposited on one of the substrates 1 forming a liquid crystal display, the full reflection layer has some portions removed so as to form light transmission portions 2a and light reflection portions 2b by etching, and color filters 3 are provided on the light transmission portions and the light reflection portions.
When the display is in a dark place, a bright image is obtained by turning on the backlight and using light irradiated through the light transmission portions 2a. When the display is in a light place, a bright image is obtained by external light reflected by the light reflection portions 2b made of the full reflection layer 2.
In the case of utilizing the full reflection layer 2 having the light transmission portions 2a partly formed therein, when the color reproduction properties are set to meet the requirements for the light reflection portions 2b at the time of providing the color filters, the color purity at the light transmission portions 2a degrades because of designing for reflection, which gives importance to brightness. On the other hand, when the color reproduction properties are set to meet the light transmission portions 2a at the time of providing the color filters, the light reflection portions 2b has a darker image because of designing for transmission, which gives importance to color purity.
Although one of the methods to solve this problem is that color filters are differently applied for transmission and reflection, this method needs to have different steps to provide the color filters, which is unfavorable in terms of costs.
There is a proposal wherein each of the color filters 3 is formed to have portions having different thicknesses by providing the full reflection layer 2 with a greater thickness to form a sufficient stepwise difference between a light transmission portion 2a and its adjacent light reflection portion 2b so that the light passing through the color filters 3 has substantially the same path length on either of transmission and reflection to obtain both transmission properties and reflection properties in a good fashion. However, this is not a favorable method since there is a possibility that a problem of peeling is created since stress increases by increasing the thickness of the full reflection layer 2, which is normally around 0.2 μm.
There has been known another method wherein the light passing through the color filters has substantially the same path length on either of transmission and reflection by providing a reflection film on each of projected portions of an indented surface of a light diffusion layer and by forming a hole in each of the recessed portions at the time of providing color filters on the uneven surface. However, this method is not practical since the method needs an extremely precise lithographic technique.